Cleaning machines, such as floor scrubbers and vacuum cleaners, are commonly used to remove dirt and other debris from various surfaces. The surfaces may be either soft surfaces, such as carpeted floors, or hard surfaces, such as concrete, wood, or tile floors. Typically, cleaning machines use numerous cleaning elements, such as brushes, mounted on a rotating disk or cylinder to remove dirt and debris from the surface. As used herein, "cleaning element" refers to a raised area or projection that removes dirt or other debris from a surface by frictional forces. Cleaning machines may employ a variety of liquid cleaning agents to assist in removing dirt and debris.
Brushes, and other types of cleaning elements, in cleaning machines will wear and decrease in length over time causing numerous problems. The cleaning efficiency of the cleaning elements, especially brushes, decreases as the length of the elements decreases. For example, the bristles in cleaning brushes grow stiffer as length decreases, thereby causing dirt to be "flicked" by the brush away from the suction intake of the cleaning machine. As a result, less dirt is removed from the surface. The bristles in the brush also may become spread out and/or become flattened, decreasing the degree of agitation or scrubbing of the surface and therefore the cleaning efficiency of the brush.
In light of cleaning element wear, timely replacement of the cleaning elements is an important factor in controlling cleaning costs. If cleaning elements are not replaced when overworn, the inefficiency of the cleaning machine will require increased man hours to clean the surface adequately. If cleaning elements are replaced prematurely, cleaning costs increase due to unnecessary cleaning element replacement.
These problems are a common occurrence due to the difficulties experienced by users in knowing the proper time to replace cleaning elements. The two methods commonly used to determine when to replace cleaning elements are highly inaccurate. In the first method, the user visually inspects the elements to determine the degree of wear. Users, however, typically have little experience or guidance concerning what is the maximum desired degree of cleaning element wear and often err on the side of removing the cleaning elements prematurely or when overworn. In the second method, the user times the replacement based on the cleaning machine operating hours. This method is often impractical as the operating hours of a cleaning machine often bear only a tangential relationship to cleaning element wear. The amount of cleaning element wear is dependent on not only operating hours but also the types of surfaces cleaned, the rate of rotation of the rotating disk or cylinder containing the cleaning elements, and the type of cleaning agents employed, if any. Operating hours are also difficult to track in most cases as cleaning machines typically do not record operating hours.